Tango is supposed to be 2/4. But some orchestras record 4/4. Being that the orchestra is selling hopefully to others than dancers. They find that it is difficult to have a vocalist singing in 2/4. One exception is Doris Day singing Hernandos Hideway. If you dance two walks and a progressive sidestep and a walk into a link dancing to 4/4 you are now out of phrase with the music . If the music is 2/4 you are not out of phrase.